Bourgoin-Jallieu - Australia's Richie Porte made a Tour de France statement as he romped to victory in Wednesday's 23.5km time-trial at the Criterium du Dauphine, as overall favourite Chris Froome struggled home in eighth.
BMC's Porte put in a stunning performance to beat four-time world time-trial champion Tony Martin of Germany into second and leave fellow overall contenders trailing in his wake.
"I didn't expect to either win the stage or take that much time," Porte said after the race. "It's been a long time since I've done a good time trial, so to do what I did today makes me really happy.
"I think I can go to the Tour de France in fantastic form and with a great team behind me."
Belgian Thomas De Gendt of Lotto held on to the overall leader's yellow jersey after the fourth stage, 27 seconds ahead of Porte and 51 seconds ahead of third placed Alejandro Valverde, who was also third on the stage.
Spain's Alberto Contador was seventh, two seconds ahead of Froome, and moved up to fifth overall at 1:02 with the Briton sixth at 1:04.
Reigning champion Froome had said on Tuesday that the time-trial would be "an important milestone" in the eight-stage race, which is seen as a form indicator for July's Tour de France.
"We've got a very similar kind of prologue in Dusseldorf, and a similar time-trial in Marseille at the end of the Tour. It's good practice and a good hit out ahead of that," Froome had said.
Being off the pace on a discipline in which he usually excels, and often takes time out of his overall rivals, will be a worry for three-time Tour winner Froome, who has yet to taste victory in a race this season.
Veteran Contador was satisfied with his race, but said he can still improve.
"I felt good, but I still have a margin for improvement to be totally comfortable in the time-trial," he said.
Froome had predicted Porte would do well before the stage began.
"I think that Richie is in great form," he said on Wednesday morning.
Porte flew round the course at an average speed of more than 50km/h, finishing 12 seconds faster than Martin and 24 seconds ahead of in-form Spanish veteran Valverde.
Thursday's stage looks to be one for the sprinters before the race heads to the mountains and culminates with two summit finishes at Alpe d'Huez and Plateau de Solaison, where Froome and Contador will look to reel in Porte.
Results and standings after the fourth stage of the Criterium du Dauphine, a 23.5km time-trial around Bourgoin-Jallieu on Wednesday:
1. Richie Porte (AUS/BMC) 23.5km in 28min 07sec, 2. Tony Martin (GER/KAT) at 12sec, 3. Alejandro Valverde (ESP/MOV) 24, 4. Stef Clement (NED/LNL) 28, 5. Chad Haga (USA/SUN) 32, 6. Jasha Sutterlin (GER/MOV) 32, 7. Alberto Contador (ESP/TRE) 35, 8. Chris Froome (GBR/SKY) 37, 9. Thomas De Gendt (BEL/LOT) 42, 10. Brent Bookwalter (USA/BMC) 45
1. Thomas De Gendt (BEL/LOT) 13hrs 05min 53sec, 2. Richie Porte (AUS/BMC) at 27sec, 3. Alejandro Valverde (ESP/MOV) 51, 4. Stef Clement (NED/LNL) 55, 5. Alberto Contador (ESP/TRE) 1:02, 6. Chris Froome (GBR/SKY) 1:04, 7. Brent Bookwalter (USA/BMC) 1:12, 8. Jesus Herrada (ESP/MOV) 1:15, 9. Sam Oomen (NED/SUN) 1:17, 10. Diego Ulissi (ITA/EAU) 1:22